Journal of Avian Biology最新文献

Although miniaturized data loggers allow new insights into avian migration, incomplete knowledge of basic patterns persists, especially for nightjars. Using GPS data loggers, this study examined migration ecology of the eastern whip-poor-will Antrostomus vociferus, across three migration strategies: flyover, short-stay, and long-stay. We documented migration movements, conducted hotspot analyses, quantified land cover within 1 and 5 km buffers at used and available locations, and modeled habitat selection during migration. From 2018–2020 we captured breeding whip-poor-wills from three study sites in Massachusetts and programmed GPS tags to collect data during fall and spring migration periods. Across 19 individual males (nine of them with repeated years of data), GPS tags collected 479 locations, where 30% were classified as flyover points, 33% as short-stays, and 37% as long-stay locations. We documented seasonal flexibility in migration duration, routes, and stopover locations among individuals and between years. Analyses identified hotspot clusters in fall and spring migration in the Sierra de Tamaulipas in Mexico. Land cover at used locations differed across location types at the 5 km scale, where closed forest cover increased and crop cover decreased for flyover, short-stay, and long-stay locations, and urban cover was lowest at long-stay locations. Discrete choice modeling indicated that habitat selection by migrating whip-poor-wills differs depending on the scale and migration strategy. For example, at the 5 km scale birds avoided urban cover at long-stay locations and selected closed forest cover at short-stay locations. We suggest that whip-poor-wills may use land cover cues at large spatial scales, like 5 km, to influence rush or stay tactics during migration.

The reddish egret Egretta rufescens is North America's rarest Ardeidae and is listed as ‘Near Threatened' by the IUCN, as endangered in Mexico, and as a species of conservation concern throughout much of its range in the United States. Little is known about the migratory behavior of the reddish egret. Individuals that were banded during the breeding season in Texas, USA, have been resighted away from breeding areas; however, records are limited and the extent of migration is unknown. Using GPS transmitters, we found reddish egrets breeding in southern Texas exhibited a partial migration strategy, with 39% of the marked population migrating from breeding sites. We assessed the dominance, body size, and arrival time hypotheses to better understand the drivers of partial migration. We did not find support for the body size hypothesis and found mixed support for the dominance hypothesis; both males and females migrated, and migratory status of individuals did not change across the years of study. Long-distance migrants were also larger than resident individuals. We found some support for the arrival time hypothesis; residents began breeding earlier than long-distance migrants and had moderately greater nest success. However, within long-distance migrants, an earlier arrival to breeding areas did not necessarily equate to earlier nesting or greater nest success. This study is the first to examine the migratory behavior of adult reddish egrets and assesses the dominance, body size, and arrival time hypotheses as explanations for partial migration in this species. Further, the results of this study emphasize the need for international conservation efforts.

Both conspicuous plumage ornamentation and song are well-known examples of sexually selected traits, but their interrelationship is not well known, perhaps in part because of confounding factors, including interspecific variation in ecology, habitat, morphology, and type of ornamentation. Here, using a phylogenetic comparative approach and the 69 species with available information (i.e. 96% of all 72 species), I examined the evolutionary relationship between forked tails and the presence/absence of song in hirundines (Aves: Hirundininae). Hirundines have similar ecology (e.g. aerial insectivores, social monogamy, and biparental provisioning), morphology (e.g. syrinx with nearly complete bronchial rings), and plumage ornamentation (i.e. a sexually selected forked tail), which provides a unique opportunity to examine the evolutionary associations between plumage ornamentation and song. In particular, hirundines have repeatedly lost their ornamentation, forked tails, setting up a condition to test their association with the evolutionary gain/loss of their simple song. After controlling for phylogeny and covariates, I demonstrated that song was less likely to be found in species with forkless tails than in species with forked tails. Two correlates of tail shape, sexual dimorphism in the overall plumage characteristics as a well-known proxy of sexual selection and incubation type as a measure of extrapair mating opportunity, were not positively related to the presence or absence of song, indicating the importance of forked tails, rather than their correlates. The analysis of the correlated evolution of discrete characters further supported the correlated evolution of the two traits, in which forked tails and song are maintained together and less likely to be lost under the presence of each other. The current study provided macroevolutionary support for the integrated use of visual and acoustic courtship traits.

The social and spatial organisation of avian societies is often complex and dynamic with individuals socialising with others in a local population. Although social interactions can readily be described in colonial breeders through the location of nests, social interactions regularly take place in other contexts that are often not considered. Social behaviour in the colonially breeding zebra finch, Taeniopygia guttata, has been the focus of much work in the laboratory, but very little is known about their social organisation in free-living populations, especially outside the breeding context. Here we characterise semi-permanent gathering locations, or ‘social hotspots' in the zebra finch in the wild. We determined the use of such social hotspots and the resulting group dynamics by quantifying movements to and from these locations through direct observation and by quantifying the vocal activity at these locations using acoustic recorders. We show that, throughout the day, zebra finches regularly visit these hotspots, and the hotspots are occupied for a substantial proportion of the day. Individuals typically arrived and left in pairs, or small groups, indicating that these social hotspots do not function just for flock formation. Instead, the high levels of vocal activity at these hotspots indicate that they may potentially function as local hubs for socialisation and information exchange, whilst also perhaps providing safety-in-numbers benefits to individuals during periods of resting. These findings characterise an important component of the natural social life of one of the most widely studied birds in captivity. The characterisation of these social hotspots highlights the use of landmarks by birds to facilitate social contacts, cohesion, and behaviour, in a social bird. Similar hangouts and social hotspots may be a feature of social behaviour in other multi-level aggregative species in which the fission and fusion of groups is an important component of daily life.

We examined phylogeographic patterns and cryptic diversity within the royal flycatcher, Onychorhynchus coronatus (Aves: Onychorhynchidae), a widespread Neotropical lowland forest tyrant flycatcher. A phylogeny of the six recognized subspecies was constructed from mtDNA sequence data of the NADH dehydrogenase subunit two gene, using Bayesian Inference and Maximum Likelihood methods. Phylogenetic analyses revealed high levels of intraspecific divergence within O. coronatus, supporting the existence of at least six independent lineages. The phylogenetic results uncovered the following relationships: (O. c. swainsoni [Southern Atlantic Forest], (O. c. coronatus [western Amazonia], (O. c. castelnaui [eastern Amazonia], (O. c. mexicanus [Central America], (O. c. occidentalis [Tumbesian], O. c. fraterculus [extreme northwestern South America])))). Biogeographic and dating analyses suggest that vicariant and dispersal events acted across approximately six million years to influence lineage diversification within this genus. Some of those events include the formation of the Amazon River and its tributaries, Andean uplift, and climatically induced vegetational shifts. Phylogenetic and biogeographic analyses of O. coronatus lineages support a hypothesis of area relationships in which the first divergence event isolated the Southern Atlantic Forest from Amazonia during the Late Miocene/Early Pliocene. This event was followed by the split of western and eastern Amazonia at the Early/Late Pliocene, the divergence of cis- and trans-Andean lowland regions also at the Early/Late Pliocene, the split between Central America and the extreme northwestern South America/Tumbes at the Early/Middle Pleistocene, and the split between extreme northwestern South America and Tumbes at Middle/Late Pleistocene. Subsequent divergence of the southern and northern populations in the western and eastern Onychorhynchus lineages took place during the Pleistocene. Comparison of phylogenetic trees and patterns in Onychorhynchus with those from published work suggests that across large New World radiations such as the Suboscines, some co-distributed lineages began to diverge long before others, which exemplifies the complexity of their evolutionary history.

When evaluating avian reproduction, life history theory examines the trade-offs between parental effort, the number and size of offspring, and the rate of nestling development. The growth rates and body sizes of developing birds vary geographically and can diverge with both latitude and migratory strategy. In terms of offspring size, growth rate can deviate in nestlings of the same or similar species due to the correlated influences of weather events, predation pressure, food availability, number of nestmates and parental provisioning. Furthermore, a longer photoperiod for species nesting at higher latitudes increases the duration over which a nestling can be fed each day, and increased nestling provisioning has been positively correlated with growth rate. Whether the amount of time a bird is fed during development drives this variation in growth rate and morphology is unknown. By removing supplemental environmental stressors (e.g. weather, predation) and standardizing feeding rate and environment, we explored the influence of daily duration of nestling provisioning on dark-eyed junco Junco hyemalis nestlings. We hand-reared 65 chicks of a sedentary junco subspecies J. h. carolinensis under both their natural photoperiod and the longer photoperiod of a closely related migratory subspecies J. h. hyemalis and compared growth rate, mass, morphology and the amount of food consumed. Average growth rate, fasted mass, wing length and total daily food consumption were all greater in birds hand-reared under the longer, more northern photoperiod treatment. These findings suggest that increased daily photoperiod at higher latitudes may allow for greater total food provisioning and thus may play a role in the ability of parents in compressed breeding seasons to produce high quality offspring. This points to a trade-off between provisioning effort and nestling growth rate in lower latitude (shorter photoperiod) populations and points to an important role of developmental plasticity on growth rate and morphology.

Bårdsen, B.-J. and Bustnes, J.O. (2022), Multiple stressors: negative effects of nest predation on the viability of a threatened gull in different environmental conditions. J Avian Biol, 2022: e02953. https://doi.org/10.1111/jav.02953

Unfortunately, we discovered that we misspecified the matrix model in our recently published article (Bårdsen and Bustnes 2022). This error did not change our overall conclusions or the original article's empirical analyses (i.e. the input values). Here, we highlight the effect of this mistake with reference to the different sections of the original article (using the same headings as in the earlier article).

The Supporting information was also incorrect and is now corrected.

We apologize for these errors.

Unaffected by the change in the model.

For an avian migrant, refueling capacity attainable during stopovers governs the entire migration schedule and, ultimately, its fitness. Specifically, timely replenishing energy stores is critical when migration involves crossing ecological barriers, within which refueling may be limited. Here, we tested the hypothesis that fuel deposition rates (FDRs) of migratory passerines within barrier-edge stopover sites are constrained by the density of potential competitors, irrespective of migration season, phenology, and local environmental conditions. We also evaluated diverse intra- and inter-specific competition scenarios and explored a potential mediation of density-dependence by environmental factors. The analyzed data, collected by us over 13 consecutive years (2009–2022), contain information on seven species of long-distance migratory insectivorous passerines measured within eight desert-edge habitats throughout autumn and spring migrations. As predicted, our analyses revealed negative density-dependence regulation of FDRs, consistent across species and migration seasons. Notably, bird density exerted its effect above and beyond the other factors known to influence FDR, such as relative ambient temperature, phenology, temporal progress of stopover, and body mass next to landfall. As expected, FDR increased at higher relative ambient temperatures and with the stopover's progress. In spring, FDR also rose as the season advanced. These findings signify the substantial impact of competition on the refueling performance of migratory passerines during their stopover on an ecological barrier's edge, acting over and above the other environmental factors. The detected importance of competition and its interrelation with other predictors provides an insight into stopover's functioning; environmentally imposed and inescapable interspecific interference is thus a significant limiting factor of FDR, a deleterious relationship potentially remediable by informed habitat restoration and planning.

Gathering demographic information on rare species is critical to understanding their population dynamics and implementing efficient conservation measures. Using integrated models, we jointly analyzed multiple data sets, including capture–recapture, GPS tracking and nest monitoring data collected over the last 10 years, to provide the first demographic insights for one of the world's rarest raptors, the endemic Reunion harrier Circus maillardi. We estimated key demographic rates including annual survival and breeding parameters (clutch size, hatching and fledging success), and used population projection models to assess population growth rate and quasi-extinction risk. In order to guide future conservation actions for the population, we evaluated the effects of different management scenarios that improve survival, fecundity, or both, on population growth and quasi-extinction risk. Comparison of the estimated annual survival (juvenile and subadult survival: 0.66; adult survival: 0.71) and breeding parameters (clutch size: 2.3; hatching success: 0.45; fledging success: 0.83) with those of other harrier species suggests that adult survival and breeding parameters of Reunion harriers are low. A small data set collected 40 years ago suggests that the probability of an egg producing a fledgling was higher and has declined to the current low level. The population models project that the Reunion harrier population is declining and faces a high risk of quasi-extinction in the next 40 years. Only management measures that simultaneously improve adult survival and fecundity could lead to a recovery of the population. These alarming results call for immediate conservation action aimed at rapidly improving the demographic rates.